DENVER  The "big-duh" secret to beating the Colorado Rockies at Coors Field, of course, is keeping the ball out of the thin air. Throw grounders, grounders, grounders. And more grounders.

And that’s what sinkerballer Jason Marquis was getting. Grounders galore. Groundballs by the gross.

But it also goes without saying – and often does – that you have to have your teammates handle the aforementioned grounders. That’s where things really started going awry for Marquis and the Padres in a 5-2 loss to the Rockies, who were celebrating their home opener with mile-high hopes that they won’t be the worst team in the National League West Division again.

At Coors Field were the two clubs not expected to be involved in a three-way race for the NL West title. Colorado's coming off a 64-98 record, though amazingly enough, that kept the Rockies as the only current major league team that's never endured a 100-loss season. The general wonder this year is whether the Rockies -- who can bang with anybody, in any ballpark, when healthy -- can pitch their way past San Diego.

Do not misunderstand, either. For all the importance of grounders and glovework Friday,the longball continued to be a major problem for Padres pitching. Solo shots by Wilin Rosario and Dexter Fowler brought the total against San Diego to seven in the first three games and four innings of 2013.

Conversely, even while playing just one of their four games at Coors Field, the Rockies lead the majors with 10 home runs. But while homers are largely indefensible, grounders aren’t, and it was with their fielding that the Padres first got into trouble for three unearned runs.

Marquis had the Rockies pounding almost everything into the infield grass from the start, which is how he became the rare All-Star pitcher for the Rockies in 2009.

With the Padres holding a 1-0 lead after just four batters, a ground-ball single by Chris Nelson skittered past substitute first baseman Jesus Guzman to start a three-run outburst, all of the scores unearned. Marquis had two outs and got a routine grounder from Josh Rutledge to charging shortstop Everth Cabrera, who never really got a handle on the ball as Nelson came across the plate to tie.

"I needed to go fast to get to the ball, but I needed to go slower when I got to the ball," said Cabrera. "That's why I got the bounce off the glove. It's tough, because if I catch that ball, it changes the game."

Both Marquis and manager Bud Black came to Cabrera's defense afterwards.

"It's a hard charge, a fast runner, a do-or-die play," said Black. "If he makes the play, it's a great play."

That, in a nutshell, is the life of a sinkerballer.

"It's happened over my career I don't know how many times," said Marquis. "But we're a team. We pick each other up. There are going to be times when they make great plays to get me out of trouble. I know Cabby feels bad about it. I know I feel bad out it, too.

"It's a physical mistake. They happen. You can control your mental mistakes. Physical mistakes are going to happen."

Actually, Marquis cited a couple of decisions of his own that he'd like back, and all of them involved him getting away from a sinkerball that was working to a slider that wasn't. All three of the Rockies big hits came on sliders. All three were put in the air.

Following a walk to Carlos Gonzalez, Tulowitzki went airborne for a two-run double. The next inning, Rosario really skied one off Marquis, a solo homer well into the left field seats of sold-out Coors Field. And then Fowler went deep for his third of the year.

Clearly, the Padres can’t compete with the Rockies or anyone else in the division in power, especially with RBI leader Chase Headley on the disabled list for another two weeks to a month.

Getting as many of his reserves into opening-week games as possible – but also loading up his lineup with right-handed hitters to face lefty Jeff Francis -- manager Bud Black started Guzman at first base in place of Yonder Alonso. That paid an immediate dividend when Guzman looped a ball into shallow left, scoring Cabrera from second for a 1-0 lead, the kind that stands little chance of standing up at Coors Field.

The Padres added an unearned run of their own in the eighth, Cabrera scoring on Carlos Quentin's double, but then the Padres effectively made an error of sorts on offense.

With two outs, the Rockies up by three and Quentin on second, rookie Jedd Gyorko hit a screaming liner over short that Tulowitzski went high to glove. The ball popped out, however, but Gyorko had stopped in his tracks in the mistaken belief that he was out and the inning over. A simple toss to first, covered by the second baseman, forced out Gyorko.

"Everybody thought the ball was caught," said first-base coach Dave Roberts. "Rutledge had to take the throw from Tulowitzki because even (Rockies first baseman Todd) Helton was almost to the dugout, thinking it was caught."